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- Ermolaev, Georgy A., et al.
(författare)
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Broadband optical properties of monolayer and bulk MoS 2
- 2020
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Ingår i: npj 2D Materials and Applications. - : Springer Science and Business Media LLC. - 2397-7132. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Layered semiconductors such as transition metal dichalcogenides (TMDs) offer endless possibilities for designing modern photonic and optoelectronic components. However, their optical engineering is still a challenging task owing to multiple obstacles, including the absence of a rapid, contactless, and the reliable method to obtain their dielectric function as well as to evaluate in situ the changes in optical constants and exciton binding energies. Here, we present an advanced approach based on ellipsometry measurements for retrieval of dielectric functions and the excitonic properties of both monolayer and bulk TMDs. Using this method, we conduct a detailed study of monolayer MoS2 and its bulk crystal in the broad spectral range (290–3300 nm). In the near- and mid-infrared ranges, both configurations appear to have no optical absorption and possess an extremely high dielectric permittivity making them favorable for lossless subwavelength photonics. In addition, the proposed approach opens a possibility to observe a previously unreported peak in the dielectric function of monolayer MoS2 induced by the use of perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS) seeding promoters for MoS2 synthesis and thus enables its applications in chemical and biological sensing. Therefore, this technique as a whole offers a state-of-the-art metrological tool for next-generation TMD-based devices.
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| 2. |
- Georgiadis, Marios, et al.
(författare)
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Nanostructure-specific X-ray tomography reveals myelin levels, integrity and axon orientations in mouse and human nervous tissue
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Myelin insulates neuronal axons and enables fast signal transmission, constituting a key component of brain development, aging and disease. Yet, myelin-specific imaging of macroscopic samples remains a challenge. Here, we exploit myelin’s nanostructural periodicity, and use small-angle X-ray scattering tensor tomography (SAXS-TT) to simultaneously quantify myelin levels, nanostructural integrity and axon orientations in nervous tissue. Proof-of-principle is demonstrated in whole mouse brain, mouse spinal cord and human white and gray matter samples. Outcomes are validated by 2D/3D histology and compared to MRI measurements sensitive to myelin and axon orientations. Specificity to nanostructure is exemplified by concomitantly imaging different myelin types with distinct periodicities. Finally, we illustrate the method’s sensitivity towards myelin-related diseases by quantifying myelin alterations in dysmyelinated mouse brain. This non-destructive, stain-free molecular imaging approach enables quantitative studies of myelination within and across samples during development, aging, disease and treatment, and is applicable to other ordered biomolecules or nanostructures.
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